In general, the Internet protocol (IP)—which has inherent advantages such as high bandwidth efficiency, low cost, robustness, and scalability—has become the generic protocol that is typically used for data transport across communication networks. In many cases, however, IP also has associated disadvantages, such as location-based routing of IP lacking compliance with user mobility, best-effort forwarding of IP failing to support differentiated services with service-specific charging and quality-of-service (QoS) enforcement, and lack of support for overlay networks such as Virtual Private Networks (VPNs).
While at least some standards bodies (e.g., Third Generation Partnership Project (3GPP), 3GPP2, Internet Engineering Task Force (IETF), or the like) have introduced protocols (e.g., Mobile IP, Generic Transfer Protocol (GTP), IP Security (IPsec), and the like) to create overlay networks on top of the IP forwarding infrastructure, such overlays networks tend to introduce many types of specialized nodes (e.g., Home Agents (HAs), Foreign Agents (FAs), Radio Network Controllers (RNCs), NodeBs, Serving General Packet Radio Service (GPRS) Support Nodes (SGSNs), Gateway GPRS Support Nodes (GGSNs), eNodeBs, Serving Gateways (SGWs), Packet Data Network (PDN) Gateways (PGWs), Mobility Management Entities (MMEs), security gateways, other types of gateways, and the like) which define the tunnel endpoints that form the overlay networks on top of the IP forwarding infrastructure.